Answer this question truthfully
### Question: What causes Corneal ulcer?
### Response: Corneal ulcers are most commonly caused by an infection with bacteria, viruses, fungi or parasites. Because bacteria can more easily penetrate a damaged cornea than a healthy one, a corneal ulcer is more likely to occur after some type of injury or trauma to the eye (e.g. tiny scratches from foreign particles that enter the eye).
Inappropriate contact lens wear (e.g. wearing the lenses overnight or not using proper hygiene when handling the lenses) may also lead to a corneal ulcer. Furthermore, a contact lens may damage the cornea as it scratches against the surface upon removal, thereby allowing easier bacterial penetration. Examples of viruses, fungi, and parasites that can cause corneal ulcers are:
Herpes simplex - This virus can lead to herpes simplex keratitis, which is a serious viral infection that may cause repeated attacks that are triggered by stress, exposure to sunlight, or any condition that impairs the immune system.
Fusarium - These fungi have been associated with fungal keratitis. The infection can occur after a corneal injury involving plant material, such as from a tree branch, or in immunosuppressed people.
Acanthamoeba - These parasites can lead to acanthamoeba keratitis mostly in contact lens users, especially those who attempt to make their own homemade cleaning solutions. It can also cause problems for people who wear their contact lenses while swimming.
Other causes of corneal ulcers include:
Abrasions (scratches) Foreign bodies in the eye Inadequate eyelid closure Severely dry eyes Severe eye allergies Various inflammatory disorders Chemical burns that can injure the cornea